Today, copying machines, facsimile machines, printing apparatuses, etc., are indispensable for paperwork in offices. These copying machines, facsimile machines, printing apparatuses, etc., are each configured based on an image recording apparatus. Recently, an image recording apparatus is drawing attention as a multi-function peripheral incorporating all the functions of a copying machine, a facsimile machine, a printing apparatus, etc. The image recording apparatus includes as a basic function of recording an image such as characters and charts onto a recording medium such as recording paper in the form of a sheet. Recording of an image can be recording of a monochrome image and recording of a color image.
Recently, due to the increase of the amount of the paperwork, improvement of the processing speed of the image recording apparatus is demanded to the above image recording apparatus. Because an image recording apparatus is an apparatus that records an image, the improvement of the processing speed is, in other words, improvement of the speed of recording onto a recording paper sheet that is a recording medium and ejecting the paper sheet. Therefore, improvement of the number of sheets of recording paper that are recorded and ejected per unit time is demanded.
In response to such demand, in addition to a method of facilitating the improvement of the processing speed of the image recording apparatus itself, a, method of improving the processing speed comprehensively by using a plurality of image recording apparatuses can be contemplated. To cope with the above demand in such a viewpoint, various proposals have been made (see, for example, Japanese Laid-Open Patent Publication Nos. H01-112275 and H08-305221).
Japanese Laid-Open Patent Publication No. H01-112275 describes an image forming apparatus that includes both of a color image forming apparatus and a monochrome electronic photograph apparatus.
Japanese Laid-Open Patent Publication No. H08-305221 describes a technique that facilitates the improvement of the processing speed by configuring a color printing apparatus using a plurality of color image forming apparatuses and adapting the color printing apparatus to configure the color image forming apparatuses to output continuously a large amount of prints and eject the prints at a high speed placing the prints in order of page number thereof on bins in a common sorter by controlling the printing process in each color image forming apparatus. The color printing apparatus described in Japanese Laid-Open Patent Publication No. H08-305221 operates two color image forming apparatuses simultaneously to improve the speed of the processing thereof.
Generally, an image recording apparatus is caused to process at one time one image recording job that executes a series of image recording processes, that is, one image recording job that executes image recording consecutively of images each of which is independent for each page onto a plurality of recording paper sheets in order of page number. In this regard, same procedure as above is also taken in a color printing apparatus described in Japanese Laid-Open Patent Publication No. H8-305221 that is configured using a plurality of color image forming apparatuses to facilitate the improvement of the processing speed thereof. That is, the color printing apparatus described in Japanese Laid-Open Patent Publication No. H8-305221 processes one image recording job at one time. The apparatus facilitates improvement of the processing speed thereof by processing in a distributed manner using a plurality of color image forming apparatuses. Therefore, the plurality of image forming apparatuses configuring such a color printing apparatus must be all the same type of apparatuses, that is, color image forming apparatuses.
In the conventional image recording system including a plurality of image recording apparatuses such as above Japanese Laid-Open Patent Publication No. H01-112275 and H08-305221, if a print job is not accepted for a predetermined time period after the system is started, the entire system is automatically shifted to an energy saving mode to reduce energy consumption. If the system accepted a print job after the system is shifted to the energy saving mode, any one or both of the image recording apparatuses returns to a recordable state.
However, since it takes time for the image recording apparatus to return to the recordable state when a print job is accepted at the time of the energy saving mode, it is problematic that a print process cannot be performed smoothly.
Although it is envisioned to allow the both image recording apparatuses to constantly wait in the recordable state for this problem, it is not preferable from a standpoint of energy saving to maintain the wait state even when a print job is not input. Therefore, in the above image recording system, a system configuration has been needed which can accelerate a process and save energy at the same time.